DDR is not just DDR. As you could see in the table on the last page, DDR SDRAM has several parameters that usually can be altered in the BIOS. These parameters (CL, or 'CAS Latency') have quite an influence on overall performance. First of all, make sure that you get modules that run at CL2.0 rather than CL2.5. It will costs you a few bucks more, but this investment is definitely worth it, bringing approximately 2-4% performance gains along with it. This is also quite important for overclocking.

One Or Two Modules?

Generally, you should use as few modules as possible. This way, you can be sure of getting the fastest timings possible. Second, your upgradeability remains good. Yet, if you use two or more DIMMs, please note that the 'slowest' module fixes the timing for all DIMMs! If only one of three DIMMs is low quality and/or low performance, all others will run in an equally slow mode. Our recommendation is as follows: do not buy the cheapest memory, but one that meets CL2 requirements.

An important factor that affects the maximum amount of memory modules are the memory rows. Intel's 845 chipset is able to address 4 rows, resulting in the following possible memory configurations:

This table only shows the maximal memory configurations. One or two modules can be combined arbitrarily.

Before purchasing memory, it's recommended that you choose your motherboard first. If it comes with only two DIMM sockets, you should get one DIMM that has the biggest capacity that you can afford. Thus, the second socket remains empty for future upgrades. In this case, you also don't have to worry about single- or double-sidedness.

It gets much more interesting if there are three or four DIMM sockets. Now, you should set your priorities on single-sidedness. This is the only way you can make sure that all slots can be used, if it ever becomes necessary. If two single-sided modules at 256 MB each are cheaper than one 512 MB DIMM, take the two single-sided. Eventually, it does not have an impact on the overall upgradeability in the case of 4 DIMM sockets.